1. Field of the Invention
The present invention generally relates to refrigerant pressure vessels for use in refrigeration systems, such as a receiver-dryer or an accumulatordehy-drator. More specifically, this invention relates to an automotive accumulator assembly that has a unique outlet tube and to a related method of manufacturing the accumulator assembly to achieve a more tolerant product design and assembly process.
2. Description of the Related Art
The use of pressure vessels in refrigeration systems, particularly automotive air-conditioning systems, is very well known. A typical refrigeration system includes a compressor, a condenser, an expansion device, an evaporator, and conduits therebetween. Additionally, an accumulator-dehydrator or a receiver-dryer unit is also usually included as will be described below. The compressor compresses liquid refrigerant into high-pressure, high-temperature vapor or gas refrigerant (e.g. 200 PSI at 150xc2x0 F.) and outputs the gas refrigerant as a superheated vapor through a high-pressure section of the conduit to the condenser. The condenser is typically constructed in the fashion of a tube-and-fin type heat exchanger. Within the condenser, the heat of the gas refrigerant flows through tubes and is released to or absorbed by outside air flowing around fins in contact with the tubes. As the gas refrigerant loses heat to the surrounding air, the high-pressure, high-temperature gas refrigerant cools and condenses into high-pressure, moderate temperature liquid refrigerant.
Subsequently, the liquid refrigerant passes through another high-pressure section of the conduit to the expansion device, which expands the compressed liquid refrigerant, thereby further cooling the liquid refrigerant into a low-pressure, low temperature liquid/gas refrigerant mixture (e.g. 40 PSI at 50xc2x0 F.). Subsequently, the cooled liquid/gas refrigerant mixture is conveyed from the expansion device to the evaporator through a low-pressure section of the conduit. The evaporator is also typically constructed in accordance with a tube-and-fin type heat exchanger. Within the evaporator, the liquid/gas refrigerant mixture absorbs heat from fan-blown air passing around fins of the evaporator. The fan-blown air is thereby cooled and passed into a living space to be cooled. As the liquid/gas refrigerant mixture absorbs heat from the surrounding ambient air, the low-pressure, low-temperature liquid/gas refrigerant mixture warms and evaporates into a low-pressure, low-temperature gas refrigerant. The gas refrigerant is then conveyed back to the compressor through a final section of the conduit to complete the circuit of the refrigeration system.
In most refrigeration systems, it is common to use one or the other of a receiver-dryer or an accumulator for various benefits. A receiver-dryer is typically located at the outlet end of the condenser in the pressure-side section of the refrigeration circuit. In contrast, an accumulator-dehydrator is typically located at the outlet end of the evaporator in the suction-side section of the refrigeration circuit. The receiver or accumulator is used for i) removing water from the refrigerant fluid, ii) screening out particulate matter, and iii) acting as a reservoir for the refrigerant fluid when refrigeration system demand is low. Additionally, an accumulator is used for iv) lubricating gaseous refrigerant with a prescribed amount of lubricating oil, and v) separating moisture-laden, partially vaporized refrigerant fluid into a moisture-free refrigerant vapor having a certain lubricating oil content. For an accumulator, it is important to separate and lubricate the refrigerant so as to provide a lubricated moisture free gas refrigerant to the inner workings of the compressor to keep the compressor in proper working condition.
It has been a major challenge in the prior art to design and manufacture such devices that operate efficiently and that are inexpensive and easy to manufacture. Traditionally, a receiver-dryer or accumulator-dehydrator is made of metal components, often aluminum, that have a sufficiently high strength to withstand the relatively high pressure within the refrigeration circuit. Within typical receiver-dryers and accumulator-dehydrators there are some similar components. Of primary concern are outlet tubes and oil pickup filters attached thereto. Various types of outlet tubes and oil pickup filters therefor have been used in refrigerant vessel designs for many decades. Such systems typically include the outlet tube having an open intake end disposed in an upper gaseous portion of the accumulator above the level of any liquid refrigerant therein. Some outlet tubes extend downwardly from the open intake end and are U-shaped such that an intake leg extends roughly parallel to an outlet leg of the outlet tube. Other outlet tubes, such as used in refrigerant receivers, have their open intake end disposed proximate the bottom of the receiver that terminates in a filter unit. Still other outlet tubes are of single-leg, dual-channel design having a downflow channel and an upflow channel disposed side by side, wherein the outlet tube terminates in a filter unit disposed in a distal portion of the vessel.
It has long been known that it is important with all of these designs that the pickup filter be located at or as near the bottom of the accumulator as practicable. For example, it was taught in U.S. Pat. No. 2,953,906 to Quick to extend a capillary tube or pickup tube through an opening in a lowermost bight portion of a U-shaped outlet tube. A discharge end of the capillary tube extends upwardly into the outlet tube and an oppositely disposed intake end extends exteriorly of the outlet tube. The intake end of the pickup tube extends downwardly and terminates in a screen portion that rests on the bottom of the container for picking up a controlled amount of liquid refrigerant and oil.
Subsequently, U.S. Pat. No. 4,199,960 to Adams et al. taught an accumulator having telescoped sections of straight tubes that replace the conventional U-shaped tube to enable using a container having a smaller diameter. Adams et al. disclosed the accumulator container as having a closed bottom wall and a pair of telescoped tubes extending upwardly from the closed bottom wall. A lower end of the telescoped tubes fits within a filter or cage having a disk that rests directly on the closed bottom wall. During operation, oil in the refrigerant settles out at the bottom of the container and is picked up through the filter that rests on the bottom of the container.
U.S. Pat. No. 4,920,766 to Yamamoto et al. and U.S. Pat. No. 5,191,775 to Shiina et al. disclose a refrigerant receiver having an aspirating or outlet tube extending downwardly within the tank or receiver with the outlet tube having a strainer or filter attached thereto and resting on the bottom of the receiver. In Yamamoto et al. the outlet tube extends downwardly through the filter, wherein the outlet tube terminates in a lower end positioned inside a recessed portion or sump of the receiver. Similarly, U.S. Pat. No. 4,827,725 to Morse teaches a suction accumulator having an improved dirt trap or filter to reduce the problems of dirt particles that cause premature mechanical failure of system components. In the Morse accumulator, a conduit includes a weir forming an upflow and downflow passage. The conduit extends downwardly within the accumulator and terminates with the filter. The filter includes a bottom that is located against the bottom of the vessel.
U.S. Pat. No. 4,474,035 to Amin et al. discloses an accumulator assembly having a U-shaped outlet tube with an oil return orifice and a filter assembly at a bight portion thereof. The filter assembly includes an integral clamp portion for maintaining a secure connection of the filter assembly to the outlet tube by means of a compressive clamping force. The clamp portion is curved so that split ends thereof surround the outlet tube and integrally fasten together. The filter assembly further includes a plastic housing that is integral with the clamp portion and includes a screen therearound. A metering tube within the filter assembly extends through the oil return orifice and extends in a direction transverse to the longitudinal axis of the accumulator assembly toward a wall of the accumulator housing. Similarly, U.S. Pat. No. 4,457,843 to Cullen et al. and U.S. Pat. No. 5,201,792 to Study disclose an accumulator having a filter assembly like that disclosed in Amin et al. wherein the filter is mounted to a bottom bend portion of a U-shaped pipe. In contrast, however, the bottom bend portion of the pipe is proximate a bottom wall of the accumulator such that the filter is in direct contact with the bottom wall.
U.S. Pat. No. 4,675,971 to Masserang discloses a refrigerant container body or accumulator having a U-shaped tube disposed therein. The U-shaped tube has a bend at a bottom portion thereof with a bleed hole that is enveloped by an annular screen assembly or filter. The filter has an inside diameter that allows it to fit closely around the tube and to be located against the inside of an end wall of the accumulator. Similarly, U.S. Pat. No. 4,938,037 to Carlisle, Jr. discloses an accumulator having a horseshoe style or U-shaped suction tube located therein. A filter is securely positioned about an oil recovery hole in the tube and is maintained in position against a bottom portion of the accumulator.
U.S. Pat. No. 5,660,058 to Harris et al. discloses an accumulator having an outlet tube that extends vertically adjacent an inner wall and includes a curved portion situated in a lowermost region of the accumulator adjacent a lower wall. An oil inlet tube is located at an end wall of the accumulator and extends in a direction along the longitudinal axis of the accumulator through the outlet tube and is surrounded by a filter assembly that is retained directly against the outlet tube. The Harris et al. patent teaches the use of a sump at the bottom of the accumulator where the oil inlet tube and filter extends as far as the bottom of a portion of the accumulator wall and extends beyond the wall into a sump that has been fabricated into the bottom wall of the accumulator assembly. Harris et al. teach that this configuration enables more oil to be introduced into the outlet tube to increase oil in the refrigerant mixture.
U.S. Pat. No. 5,970,738 to DeNolf et al. teaches an accumulator having a unique oil filter unit with an extended tube for reaching lower within the accumulator to use less oil. DeNolf et al. disclose that the oil filter unit is attached to a bight portion of an outlet tube within the accumulator. The oil filter unit is similar to that disclosed in Amin et al., Cullen et al., and Study and is attached to the outlet tube by a clamp portion. An oil pickup tube within the filter extends from within the outlet tube, through an aperture in the outlet tube, and downwardly toward the bottom of the accumulator. Thus, compared to previous devices, an end of the pickup tube is extended further down into the accumulator such that it is closer to the bottom of the accumulator to reduce the amount of oil required in the accumulator.
U.S. Pat. No. 5,778,697 to Wantuck is remarkably similar to DeNolf et al. Wantuck teaches use of a metering device for an accumulator that allows oil to be drawn into a return conduit practically to the bottom of the accumulator. The return conduit includes an opening in a lowermost curved portion thereof, wherein the opening faces downwardly toward a lower end wall of the accumulator. A filter assembly, similar to that of DeNolf et al., is mounted to the lowermost curved portion of the return conduit with an oil inlet tube having one end press fit into the opening in the lowermost curved portion of the return conduit and another end that is located proximate the lower end wall of the accumulator. A screen portion of the filter assembly includes a tubular portion surrounding the oil inlet tube and a bracket to secure the screen portion to the return conduit. Similar to Adams et al., a lower end cap of the filter assembly encloses a lower end of the screen portion and is disposed in contacting relation with an inside surface of the lower wall such that the filter assembly is supported on the lower end wall of the accumulator.
Unfortunately, most of the above-listed prior art references incorporate outlet tubes of various geometries that are composed of rigid material. Use of rigid material for the outlet tube requires carefully calculating and comparing the longitudinal dimensions of the outlet tube with respect to the interior longitudinal dimensions of the vessel. This is so that during manufacture of the vessel assembly, the filter attached to the outlet tube always locates against the bottom of the vessel and that the outlet tube is never too long so as to prevent proper assembling of the vessel assembly due to an interference condition. In other words, minimum and maximum material conditions of the vessel and its closure member must be compared to the minimum and maximum material conditions of the outlet tube to develop workable tolerances for each. Some accumulators, as described in some of the above-listed references, incorporate U-shaped outlet tubes that are dimensioned and manufactured short enough to avoid such an interference condition. Unfortunately, however, such accumulators do not have the oil filter assembly located against the bottom of the vessel.
One of ordinary skill in the art will readily recognize that if the outlet tube is too long with respect to the interior longitudinal dimensions of the vessel, the vessel assembly would be prevented from assembling completely or correctly due to the interference between the longitudinal extremities of the outlet tube and the longitudinal extremities of the vessel interior. Therefore, close tolerance stackups of the outlet tube, the vessel, and a vessel closure must be carefully calculated during design, and must be closely controlled in manufacturing operations to ensure a proper assembly. While calculating and specifying such tight tolerances on paper is rather simple and inexpensive, actually controlling such close tolerances in a factory is usually complex, expensive, and sometimes cost-prohibitive.
From the above, it can generally be appreciated that the refrigerant vessel assemblies of the prior art are not fully optimized to be more efficient while being less costly and easier to manufacture. Specifically, such devices often require tight tolerances to be controlled during manufacture of components to ensure proper assembly, thereby increasing production difficulties and related costs. Therefore, what is needed is a refrigerant vessel assembly that incorporates an outlet tube that is flexible and resilient, and is dimensioned so as to take up predetermined excess length of the outlet tube when the vessel assembly is assembled so that an oil pickup filter maintains position against the bottom of the accumulator regardless of tolerance stackups of the outlet tube and other various components of the accumulator.
According to the preferred embodiment of the present invention, there is provided a vessel assembly including a vessel that has an interior portion. The vessel also includes an inside bottom surface or end and a vessel closure member is provided that defines an inside top portion of the vessel. A flexible conduit assembly is disposed within the interior of the vessel such that an upper end of the flexible conduit assembly is connected to the inside top portion of the vessel. The flexible conduit assembly further includes a distal end that is located against the inside bottom surface of the vessel. Due to the resiliency of the flexible conduit assembly, the distal end of the flexible conduit assembly stays located against the inside bottom surface of the vessel regardless of dimensional variations of the flexible conduit assembly, the vessel, and the closure member. Additionally, the present invention also encompasses a method of manufacturing the vessel assembly described above.
It is an object of the present invention to provide a pressure vessel assembly that has a more tolerant design and assembly process than prior art devices in the same class.
It is another object to provide a pressure vessel assembly wherein a filter unit locates against the inside bottom surface of the vessel assembly and an outlet tube deflects without breaking during assembly to compensate for extra length of the outlet tube compared to axial inside length dimensions of the vessel.
It is a still another object to provide a pressure vessel that is capable of being automatically assembled.
It is yet another object to provide a method for manufacturing the pressure vessel of the present invention, wherein the method is more simple and less costly than prior art methods.
It is a further object to provide a J-tube within an accumulator that flexes during assembly to comply and conform with the inside of the accumulator.
It is still a further object to provide a pressure vessel design for use in an air-conditioning system that includes a minimum number of parts, is less expensive to manufacture than prior art designs, and can be manufactured using readily available lightweight materials.
It is yet a further object to provide more efficient use of lubricating oil within an accumulator to reduce the overall cost of the air-conditioning system.
These objects and other features, aspects, and advantages of this invention will be more apparent after a reading of the following detailed description, appended claims, and accompanying drawings.